Concluding a 7-month controversy, Science publishes a paper detailing how the bird flu virus can be modified to spread through the air among ferrets.

Last December, Ron Fouchier and colleagues at the Erasmus Medical Center in
Rotterdam, the Netherlands, submitted a paper to Science detailing
their creation of a mutant strain of the avian H5N1 virus that could spread
between ferrets via airborne transmission. At the same time, Yoshihiro
Kawaoka and his team at the University of Wisconsin, Madison, submitted
similar research to Nature. A contentious debate ensued.

Last December, Ron Fouchier and colleagues at the Erasmus Medical Center in Rotterdam, the Netherlands, submitted a paper to Science detailing their creation of a mutant strain of the avian H5N1 virus that could spread between ferrets via airborne transmission. A contentious debate ensued. Source: Science

Because H5N1 is highly pathogenic in humans, killing over 60% of individuals
that become infected, the research has the
potential to be used as a biological weapon, some scientists and
policymakers argued. The journals held off publishing the papers while the
National Security Advisory Board on Biosecurity (NSABB), a US panel of
scientific and safety advisors, reviewed the work.

Within weeks, the NSABB recommended that portions
of the papers be redacted prior to publication after finding “the
potential risk of public harm to be of unusually high magnitude."
Shortly after that declaration, 39 influenza researchers around the world,
including Fouchier and Kawaoka, declared
a 60-day moratorium on bird flu transmission research. The World Health
Organization subsequently extended that moratorium.

Then, on March 30, after a meeting with flu experts and the papers’ authors,
the NSABB reversed
their decision. As a result, Kawaoka’s study was published
online on May 2 in Nature, and today Science published
the Fouchier paper in full(1, 2). In the paper, publically available for the
first time, Fouchier and colleagues describe five small changes, mutations
in the DNA, that are enough to make H5N1 transmissible in the air between
mammals.

The findings are powerful evidence that there is a “real potential” for the
bird flu virus to evolve into a pandemic-causing form, said Bruce Alberts,
editor-in-chief of Science, at a teleconference June 20 announcing
the publication. “It’s our hope that [this] publication will help to make
the world safer, particularly by stimulating many more scientists and
policymakers to focus on preparing defenses,” he added. The published text
retains all the original methods and results, Fouchier confirmed during the
announcement, though wording was added to better explain the benefits and
risks of the research.

To study how avian influenza viruses might become airborne between mammals,
Fouchier and colleagues first genetically modified the virus. After
surveying the literature for genetic changes that appeared in the 1918,
1957, and 1968 pandemics, they introduced three of these mutations into the
H5N1 virus, but found that the mutated virus did not replicate or transmit
effectively between ferrets—a popular mammalian model of flu, as ferrets
show similar flu symptoms to humans.

The researchers applied the virus directly into the noses of ferrets, waited a
bit, then swabbed the animal’s noses and used those samples to inoculate
more ferrets, “passing” the virus from one animal to another. “Already,
after a few passages, we found that the virus replicated better in the upper
respiratory tract of ferrets,” said Fouchier. After 10 passes, the virus had
acquired multiple new mutations, and with them, the ability to transmit
between ferrets via aerosol or respiratory droplets. Although airborne, the
virus was not lethal to the ferrets, Fouchier emphasized.

The team then analyzed the final viral DNA and identified several previously
unknown mutations that allowed the virus to transmit in the air. “As little
as five mutations, but certainly less than 10, are sufficient to make H5N1
virus airborne,” said Fouchier. All the mutations have been detected in the
virus in nature, just never together, said Fouchier.

Kawaoka’s paper, published a month earlier in Nature, identified
similar mutations that cause airborne transmission, but those researchers
created a chimeric virus by combining a mutated hemagglutinin protein with
genes from the H1N1 virus, which sparked a pandemic in 2009.

The research proves that H5N1 should not be taken lightly, and surveillance
programs can now watch out for the newly identified mutations in the wild,
in the hopes of stopping a pandemic before it starts. Fouchier’s team also
tested a current antiviral and an H5N1 vaccine against the mutated virus,
and found that both treatments were effective in ferrets.

The publication of Fouchier’s paper in Science was accompanied
by a study by Derek Smith and colleagues at the University of Cambridge
assessing the virus’ potential to evolve and transmit via the air naturally.
The issue also included six commentary articles on the topic, including
suggested strategies on how to prepare for an H5N1 pandemic from vaccine
manufacturers (3, 4).